An explosion at Britain's third largest oil refinery in North Lincolnshire has ignited a fire, leaving an oil worker missing.

Owners of the refinery and Emergency Services announced that the unidentified employee was working close to a distillation unit at the Lindsey Oil Refinery when it caught fire and then exploded around noon on Tuesday.

Police said two people were treated for minor injuries from the blaze at the refinery near Hull. More than 50 firefighters had to battle the blaze before containing it.

French oil giant Total, which owns the refinery, said that rescuers were also searching for the missing worker.

People living nearby reported hearing the explosion across a wide area and black smoke could be seen from eight kilometers away.

"Total Lindsey Oil Refinery... confirms that a fire occurred at 11:57 am today (Tuesday), shortly followed by a small explosion," said a company spokeswoman.

"The refinery emergency plan has been put into operation. The county emergency services are at the scene assisting the refinery's emergency response team."

The company added later in a statement that one person was unaccounted for and that the Emergency Services were continuing to search for him.

A union leader said the fire and the blast raises concerns about Total's safety measures.

"The fire started in a heater where the oil is heated to a colossal temperature," said Pail Whitehurst, of the GMB union, adding, "This brings into question Total's safety record yet again. They have to be held accountable."

The refinery, which started production in 1968, has a processing capacity of more than 200,000 barrels per day.